© 2022
8
WLD SERIES LASER DIODE DRIVERS
SAFETY INFORMATION
SAFE OPERATING AREA — DO NOT EXCEED
INTERNAL POWER DISSIPATION LIMITS
Before attempting to operate the WLD33ND driver, it is
imperative that you first determine that the unit will operate
within the
Safe Operating Area
(SOA). Operating outside
of the SOA may damage the laser and the WLD33ND.
Operating outside of the SOA will void the warranty.
To determine if the WLD33ND driver will be operating in a
safe range, follow the instructions for calculating the Safe
Operating Area online with your system’s voltages and
current requirements:
www.teamwavelength.com/support/design-tools/soa-ld-calculator/
SOA charts are included in this datasheet for quick reference
(
), but we recommend you use the online tools
instead.
!
To ensure safe operation of the WLD33ND
driver, it is imperative that you determine if
the unit is going to be operating within the
internal heat dissipation Safe Operating
Area (SOA).
If you have any questions about the Safe Operating Area
calculator, call the factory for free and prompt technical
assistance.
THERMAL MANAGEMENT KITS
The WLD Series of laser diode drivers have many thermal
management accessories. They include thermal washers,
heatsinks, and fans. These products are available either as
individual accessories, or bundled together in kits. The use
of these thermal management accessories helps ensure
that the WLD will remain in the SOA during operation.
THEORY OF OPERATION
The WLD Series drivers are voltage controlled current
sources: they deliver the current commanded by the
setpoint. The control system continually monitors the actual
output current, compares it to the setpoint, and adjusts the
current if there is a difference between the two signals.
It may be useful to remember that you do not directly set
the drive current setpoint; instead, you adjust a voltage
signal that represents the output current. The voltage and
output current are related by a transfer function that varies
by driver model number and maximum current.
The setpoint voltage is adjusted at Pin 2 (V
SET
). In standalone
operation, this is the only way to vary the setpoint. If using
the evaluation board, there are trimpots that can also adjust
the setpoint.
The adjustable current limit is set by choosing the resistor
R
LIM
in standalone operation, or with a trimpot if using the
evaluation board.
As current is driven through the laser diode load, there is
a voltage drop across the load because of its impedance.
As the current increases, the voltage drop may increase to
the point that it reaches the Compliance Voltage limit of the
current source. Once that occurs, the current source is no
longer able to increase the current driven to the load even if
you increase the setpoint.
The WLD drivers include features that help protect your
laser and make the driver more versatile in a wide array of
applications:
• The user-adjustable clipping current limit protects the
laser from over-current situations by never allowing
the output current to exceed the user-set limit. If the
setpoint is greater than the limit, the WLD will hold the
output current at the limit.
• Operate in Constant Current or Constant Power mode.
Constant Current keeps the current through the laser
diode constant, while Constant Power keeps the current
through the monitor photodiode constant (proportional
to output power).
• Output current switches on after a 250 ms overall delay
from the time the enable signal is applied.
•
The ENABLE pin must be held low or left floating in
order to have current enabled from the laser driver. To
disable output, connect greater than 3 V to Pin 1.
• Low leakage current, excellent for VCSELs.
